A television picture is a one dimensional time series signal made into a two dimensional picture by scanning, and which becomes to be seen as a timely and spatially continued picture by a time and space integral effect of eyesight. Accordingly, when every second's picture numbers is little, the time integral effect is not sufficient whereby plane flicker is occurred, and when the scanning line numbers is little, the spatial integral effect is not sufficient whereby it becomes a rough picture so that scanning lines are seen by eyes. The interlaced scanning system such as NTSC system is directed to reduce a plane flicker by making every second's picture numbers to be many, but relative to the picture of non-interlaced scanning system of 525 scanning lines which is doubled the scan, the spatial integral effect is decreased, and the picture becomes rough whereby it becomes seen to eyes.
Thus, as a scanning line numbers doubling method for solving the problems such as line structure and vertical resolution deficiencies occurred due to lack of scanning line numbers, an intra-field interpolation system for interpolating by averaging upper and lower scanning lines of scanning line to be interpolated, and an inter-field interpolation system for interpolating by a scanning line of previous field of the scanning line to be interpolated, are offered. And, recently a motion adaptive interpolation system is offered which executes the interpolation by using the intra-field interpolation system in an image region having a motion by discriminating a degree of motion within the image and executes the interpolation by using the inter-field interpolation system in the image region having no motion.
FIG. 1(A),(B) to FIG. 3(A),(B) are diagrams for respectively illustrating the aforementioned inter-field interpolation system, intra-field interpolation system and motion adaptive interpolation system.
FIG. 1(A),(B) are respectively a conceptive diagram and circuit diagram for illustrating the inter-field interpolation system. A scanning line(i) within a field(t2) to be interpolated is made by substituting a scanning line(c) within a previous field(t1). An inputted luminance signal Yin is made to a signal which is compressed to 2/1 time by a time compressor 3 and to a signal which is compressed to 2/1 time after delaying one field by a time compressor 2 and thereafter respective output clock signal is selected by switching a switch 4. A clock signal of the time compressor 2 is selected for the scanning line(i) to be interpolated while a clock signal of the time compressor 3 is selected for original scanning lines(a and b).
FIG. 2(A),(B) are respectively a conceptive diagram and circuit diagram for illustrating the intra-field interpolation system. A scanning line(i) within a field(t2) to be interpolated is made by averaging upper and lower scanning lines(a,b) within the same field(t2). A signal in which the inputted luminance signal Yin is averaged with a signal delayed it by one line by a delay element 5, summer 6, divider 7 and time compressor 8 and then compressed to 2/1 time, and a signal in which the inputted luminance signal Yin is compressed to 2/1 time by a time compressor 9, are made, and thereafter respective output clock signal is selected by switching a switch 10. The clock signal of the time compressor 8 is selected for the scanning line(i) to be interpolated while the clock signal of the time compressor 9 is selected for original scanning lines(a and b).
However, there has been a problem that in the inter-field interpolation system, in case of image having a motion, a shimmering phenomenon and step edge phenomenon are occurred whereby a picture quality reduced, while in the intra-field interpolation system, a signal to be used for the interpolation is made by an average of two scanning lines whereby a vertical resolution is decreased.
That of recently offered in order to solve the problems occurred in the aforementioned systems is a motion adaptive interpolation system shown in FIG. 3(A),(B). An inputted luminance signal Yin is made to a signal to be used for an interpolation of a scanning line(i) within a field(t2) to be interpolated by an intra-field interpolator 11 and an inter-field interpolator 12 and thereafter a motion detecting section 13 judges a motion within the inputted image and then a pixel to be interpolated within a region corresponding to the motion region is interpolated by using an image signal made by the intra-field interpolation system. A pixel to be interpolated within a region having no motion is interpolated by using an image signal made by the inter-field interpolation system. The output signals of the interpolators 11 and 12 in accordance with the switching state of a switch 14 is used for a scanning line(i) to be interpolated by being compressed to 2/1 time by a time compressor 16. On the other hand, a signal in which the inputted luminance signal Yin is compressed to 2/1 time by a time compressor 15 is used for original scanning lines(a and b).
The motion adaptive interpolation system operating as this principle exerts a relatively better performance in case of judging well the motion of the inputted signal, but an exactness of the motion judgement is lowered for a complex video signal mixed with the luminance signal and chrominance signal. Accordingly, in case when if judging with respect to the inputted signal having a motion as a region having no motion, an error would be occurred in the interpolation whereby a remarkable picture quality deterioration phenomenon such as a shimmering, step edge or motion blur would be occurred, while in case when if judging with respect to a region having no motion as a region having a motion, a problem such as a vertical resolution decrease is occurred.
And, in the interpolation system also, since only pixels of upper and lower of the pixel same vertical position to be interpolated or pixels of horizontal positions of previous and later field are used, aforementioned conventional interpolation systems are difficult to do an exact scanning line interpolation in case when a video signal of image region having a motion has a detail of vertical direction or diagonal direction. Moreover, there has been a disadvantage that a confrontation is in lack for the region having a successive motion.